There’s a new documentary on PBS called “The Music Instinct: Science & Song.” It’s co-hosted by musician Bobby McFerrin and neuroscientist Daniel Levitin and they spend almost two hours exploring the elements and building blocks of music, musical universals across time and cultures and the possible evolutionary roots of music. The program also answers questions about the healing power of music for stroke victims and Parkinson’s patients and how playing music changes the musician’s brain for the better. Levitin walks us through the program and through his own research and findings. He’s a musician himself, a cognitive psychologist and neuroscientist at McGill University in Montreal. Levitin is also the best-selling author of “This is Your Brain on Music” and more recently “The World in Six Songs.”